Imagine a world with no tweets, no emails, no notifications pushed to your phone. A world without Candy Crush or indeed, even Facebook; a land without the Internet.

From physical destruction to hack attack to the iron first of the government, we examine whether or not it's possible to flip a kill switch

Imagine a world with no tweets, no emails, no notifications pushed to your phone. A world without Candy Crush or indeed, even Facebook; a land without the Internet.

The thought may sound like heaven to minimalists, but in recent months, dictators around the world have been all too willing to transform the idea into a hellacious reality, flipping a switch and completely disconnecting whole nations from the Web: Syria. Egypt. Libya. All have been plunged into darkness during periods of civil unrest.

But is there any way the United States could be disconnected from the Internet? Could an act of terror, war, or simple governmental dictatorship snatch away our social feeds and online gaming? Curious, I reached out to several experts to examine all the potential doomsday scenarios.

Physical attack on the tubes

They say the Internet is a series of tubes. One obvious way to disconnect the United States from the rest of the Net would be to cut, blow up, or otherwise destroy those tubes, right?

Not so fast. As it turns out, you'd need to cut a lot of tubes to completely disconnect the U.S. from the Internet. Check out the map below of all the undersea cables that connect the country to the outside world. Now, consider that TeleGeography's map lists only undersea cables (which you can peruse here), and doesn't include the legion of wires that connect the U.S. to Canada and Mexico over land. And what about wireless networks?

Yeah, you're starting to get the picture. Disconnecting all of America's tubes just isn't going to happen.

"It's close enough to impossible that in realistic terms, it's unlikely to the point of irrelevancy," says Patrick Gilmore, the chief network architect at Akamai, a content delivery network estimated to be responsible for up to 20 percent of all Web traffic. The good news doesn't end there.

"Even if you could do that, a lot of the reason things were done like that in Egypt and Syria were to keep people from posting to social networking sites," Gilmore continues. "Many of those social networking sites are hosted here in the United States. So if you could wave a magic wand and disconnect the United States, people would still see all those posts from each other inside the United States. It wouldn't stop that from happening."

Score one for free speech.

Hack attack on the servers

If the tubes are the veins of the Internet, the servers that power the Net are its brains. Could hackers use their botnets and evil geek powers to send America spiraling offline?

"That's actually much more likely than a physical attack, I think," says Dorian Kim, VP of IP engineering and network development for NTT Communications, the second-largest Internet backbone provider in the world. "...The entire wiring system relies a great deal on various systems of trust. It's possible for somebody--especially someone who is kind of an insider at an ISP or telco--to do things that would disrupt the infrastructure in a pretty widespread way."

There are several caveats to that, however. Any hack attack of that magnitude would very likely extend beyond U.S. shores, for one thing. It would be very difficult and take a high level of technical ability to accomplish. And it wouldn't last very long, either: Given the decentralized nature of the Net, Kim says the disruption would likely be limited to hours, or a day or two maximum.

Even if hackers managed to wreak havoc on the U.S. Internet, all the experts I spoke to expressed extreme doubt that an attack would be able to take out the entire country.

"Let's take the CloudFlare attack," says Gilmore, referring to a DDoS attack in Europe a few months ago that CloudFlare mitigated. "I was quoted in The New York Times as saying it was the largest publicly disclosed attack in the history of the Internet. That was 300 gigabits, or 300 billions. The total traffic on the Internet is measured in many, many terabits--trillions. And the U.S. is a large portion of that. A 500-gigabit attack--which again, would be the largest attack ever--would not be able to disrupt even a large portion of the United States.

"Some networks would go down," he continues. "You might be able to take out an ISP in a city, and have that ISP go offline, but to take 25 or 50 percent of the U.S. offline? It's not impossible to do, but it'd just be so ridiculously difficult."

Individual things--specific ISPs, websites, and so on--would be much easier to attack, says Gilmore. Kim agrees: The Internet's backbone carriers are just too strong to hack with any sort of effectiveness.

"[Hackers] would be much better off going for the softer underbellies of companies than going after core infrastructure," he says.

The Man holding you down

So, widespread tube cutting and hack attacks would not only be incredibly difficult to pull off, but they would also be of questionable effectiveness. Now, let's explore the darkest of these dark options. The Middle Eastern countries mentioned above disappeared from the Net thanks to the heavy hands of iron-fisted dictators. Is there any way the U.S. government could possibly do the same? Does the Man have an Internet kill switch?

"No, there's no legal authority for it," says Dan Auerbach, a staff technologist with the Electronic Frontier Foundation. "Even if some were invented through creative lawyering, the practical reality is that it would just be too difficult to do in any sort of short time frame."

This circles back to the United States' dense web of tubes, and all three experts I spoke to touched on this point. Small countries like Syria have very few Internet access points, and very few service providers maintaining those access points, making it trivial for the government in such nations to shut down the hardware. That ain't so in this country.

"In the U.S., by contrast, we don't have that sort of monolithic ISP space," says Auerbach. "We have many different networks, and within those networks, there are many types of subnetworks operating. The amount of machinery you would need to shut down is enormous and controlled by lots of people. It'd be really hard to do that in any sort of quick way."

And again, the headaches double when you add wide area and cellular networks to the mix. Safe to say, in the States, The Man isn't going to shut us all down.

Built to last?

So, rule out the tubes, the hackers, and The Man. What might be the most effective way to wreak havoc on the country's infrastructure? NTT's Dorian Kim has an idea.

"Most of the networks--whether you're talking about networks like NTT, Level 3, AT&T, or content distribution people like Netflix or Akamai--all their traffic tends to get exchanged in a very small number of 'carrier hotels' in cities around the country," Kim says.

"The number of those concentration points of activity that you'd need to knock out to do serious damage to the Internet is actually smaller than the number of submarine cables," he continues. "If you ... take out, oh, half a dozen of these around the country, you'd actually do serious damage to the infrastructure. And if you double that and take out the dozen biggest carrier hotels, the impact will be very severe."

And therein lies the Internet's biggest weakness. The great big Web's decentralized nature makes it incredibly resistant to attack, but when you get down to brass tacks, all the mininetworks that make the whole have to hook up somewhere.

"A lot of this comes down to the fact that there are economics behind how networks are built," Kim says. "You have to think about concentration points based on population, and with insulated networks, it makes sense for people who have to interconnect to be as close to each other as possible... Eventually, you wind up in a metro area with one or two gigantic carrier hotels where everybody's congregated."

Built to last

But don't let that fool you: Pulling off an attack of that nature would be very difficult indeed, and its impact would be felt far and wide, not just in the United States. If--if--a large, well-informed, well-trained, and well-equipped team were able to pull off such a feat, it would be a direct attack against the entire world.

Let's pull it back a bit. Thanks to its central role on the Net and its decentralized network infrastructure, the odds of the U.S. pulling a Syria and disappearing from the face of the Web are effectively nil. In fact, when Renesys--a leading network research firm--examined how difficult it would be for countries all around the world to be disconnected from the Net, the U.S. was ranked "Resistant." Not Average. Not even Low Risk. Resistant. (See the map above.)

So breathe easy, folks. For all intents and purposes, if you're in the States, you've got mail--and nothing is ever going to take away the Internet in a flash. Unless, of course, you forget to pay your bill.